No description available.

No description available.

Please read the abstract in the section 00front of this document / Dissertation (MEng (Mechanical Engineering))--University of Pretoria, 2006. / Mechanical and Aeronautical Engineering / unrestricted

A market for a low-cost vibration protection device in the rotating machine industry has been identified that satisfies the needs of small firms unable to afford and sustain a condition monitoring operation. In this project, a system is developed that satisfies the need for a low-cost, conservative, configurable and intuitive device that can perform vibration measurements on a range of gearboxes and make an inference as to the level of vibrations coming from the bearings on the shafts. The inference made by the device, derived from the frequency content of the measured signal, may be used by the operator of the gearbox to make a judgment of whether to have the gearbox investigated by a competent authority. In order to assist this investigation, a vibration history of the device is stored, both in time and frequency domain formats, as well as a full history of the relevant diagnostic information. To reach this point of maturity, the project evolved through three different hardware configurations. The various iterations were tested within the scope for which they were designed and the lessons learned after each test was incorporated into the next iteration. The final iteration incorporated all the refinements of the system up to that point as well as the anticipated scope of further development into the commercial realm. To verify the inference credibility of the device, the results of the final specification of the device was evaluated against data obtained from the condition monitoring department of SASOL in Secunda. The results were analysed on two accounts. Firstly the signal reproduction accuracy was evaluated, which established how accurately the signal was digitized and how the processing algorithms performed. Secondly, the inference accuracy was gauged against the practices of SASOL. On both accounts, the final device performed satisfactorily. The end result of this project is considered a ‘near-commercial ready’ prototype with all the hardware on-board for user interaction, signal processing, 3rd party viewing of the data and future expandability. / Dissertation (MEng)--University of Pretoria, 2014. / tm2015 / Mechanical and Aeronautical Engineering / MEng / Unrestricted

No description available.

This research presents the development and proof of concept of a TeleGeoMonitoring (TGM) system for spatially monitoring and analyzing, in real-time, data derived from vehicle-mounted sensors. In response to the concern for vibration related injuries experienced by equipment operators in surface mining and construction operations, the prototype TGM system focuses on spatially monitoring vehicle vibration in real-time. The TGM vibration system consists of 3 components: (1) Data Acquisition Component, (2) Data Transfer Component, and (3) Data Analysis Component. A GPS receiver, laptop PC, data acquisition hardware, triaxial accelerometer, and client software make up the Data Acquisition Component. The Data Transfer Component consists of a wireless data network and a data server. The Data Analysis Component provides tools to the end user for spatially monitoring and analyzing vehicle vibration data in real-time via the web or GIS workstations. Functionality of the prototype TGM system was successfully demonstrated in both lab and field tests. The TGM vibration system presented in this research demonstrates the potential for TGM systems as a tool for research and management projects, which aim to spatially monitor and analyze data derived from mobile sensors in real-time. / Master of Science

Os principais impactos ambientais decorrentes de desmontes de rochas com explosivos estão associados à geração de vibrações no maciço circundante e pressão acústica. Para o monitoramento sismográfico apropriado, é fundamental que o sensor esteja bem acoplado ao meio, possibilitando a medição acurada da vibração do terreno. Devido à existência de diversas recomendações a respeito da montagem dos sensores de vibração (geofones) em campo, este estudo tem o intuito de avaliar os métodos de acoplamento de geofone mais comuns, determinando quais são aceitáveis para um adequado monitoramento sismográfico. Dessa forma, foi estudada a influência de quatro métodos de fixação nos parâmetros de vibração. Para este propósito, o primeiro geofone foi colocado sob um saco de areia, o segundo foi enterrado no solo, o terceiro foi cravado no solo e o quarto foi livremente colocado sobre o solo. Estes geofones foram dispostos lado a lado e as vibrações de desmontes com explosivos de uma mina de carvão a céu aberto foram monitoradas. As vibrações foram analisadas em termos de velocidade de vibração de partícula de pico, históricos temporais e frequência associada à vibração. Os resultados obtidos indicaram o desacoplamento do geofone sob saco de areia, descartando o método. O enterramento do geofone se mostrou preferível, entretanto, o uso de cravos registrou bom acoplamento. A colocação do geofone sobre o solo se mostrou aceitável de acordo com o nível de aceleração de vibração, decorrente do desmonte. / The main environmental impacts from rock blasting are ground vibrations and air overpressure. For proper blast vibration monitoring, it is critical that the sensor be coupled to the medium, enabling accurate measurement of ground vibration. Due to the existence of several recommendations regarding the mounting of vibration sensors (geophones) in the field, this study intends to evaluate the most common geophone coupling methods, determining which are acceptable for adequate vibration monitoring. The influence of four mounting methods on vibration parameters was studied. For this purpose, the first geophone was sandbagged, the second one was buried in soil, the third one was spiked and the fourth one was placed freely on the ground. These geophones were mounted side by side and ground vibrations at an opencast coal mine were monitored. The vibrations were analyzed in terms of peak particle velocity, time histories and frequency spectra. The results indicated the decoupling of the sandbagged geophone, discarding the method. The burial of the geophone proved to be preferable, however, the use of spikes recorded good coupling. The free placement of geophone proved to be acceptable according to the expected acceleration level.

Os principais impactos ambientais decorrentes de desmontes de rochas com explosivos estão associados à geração de vibrações no maciço circundante e pressão acústica. Para o monitoramento sismográfico apropriado, é fundamental que o sensor esteja bem acoplado ao meio, possibilitando a medição acurada da vibração do terreno. Devido à existência de diversas recomendações a respeito da montagem dos sensores de vibração (geofones) em campo, este estudo tem o intuito de avaliar os métodos de acoplamento de geofone mais comuns, determinando quais são aceitáveis para um adequado monitoramento sismográfico. Dessa forma, foi estudada a influência de quatro métodos de fixação nos parâmetros de vibração. Para este propósito, o primeiro geofone foi colocado sob um saco de areia, o segundo foi enterrado no solo, o terceiro foi cravado no solo e o quarto foi livremente colocado sobre o solo. Estes geofones foram dispostos lado a lado e as vibrações de desmontes com explosivos de uma mina de carvão a céu aberto foram monitoradas. As vibrações foram analisadas em termos de velocidade de vibração de partícula de pico, históricos temporais e frequência associada à vibração. Os resultados obtidos indicaram o desacoplamento do geofone sob saco de areia, descartando o método. O enterramento do geofone se mostrou preferível, entretanto, o uso de cravos registrou bom acoplamento. A colocação do geofone sobre o solo se mostrou aceitável de acordo com o nível de aceleração de vibração, decorrente do desmonte. / The main environmental impacts from rock blasting are ground vibrations and air overpressure. For proper blast vibration monitoring, it is critical that the sensor be coupled to the medium, enabling accurate measurement of ground vibration. Due to the existence of several recommendations regarding the mounting of vibration sensors (geophones) in the field, this study intends to evaluate the most common geophone coupling methods, determining which are acceptable for adequate vibration monitoring. The influence of four mounting methods on vibration parameters was studied. For this purpose, the first geophone was sandbagged, the second one was buried in soil, the third one was spiked and the fourth one was placed freely on the ground. These geophones were mounted side by side and ground vibrations at an opencast coal mine were monitored. The vibrations were analyzed in terms of peak particle velocity, time histories and frequency spectra. The results indicated the decoupling of the sandbagged geophone, discarding the method. The burial of the geophone proved to be preferable, however, the use of spikes recorded good coupling. The free placement of geophone proved to be acceptable according to the expected acceleration level.

Os principais impactos ambientais decorrentes de desmontes de rochas com explosivos estão associados à geração de vibrações no maciço circundante e pressão acústica. Para o monitoramento sismográfico apropriado, é fundamental que o sensor esteja bem acoplado ao meio, possibilitando a medição acurada da vibração do terreno. Devido à existência de diversas recomendações a respeito da montagem dos sensores de vibração (geofones) em campo, este estudo tem o intuito de avaliar os métodos de acoplamento de geofone mais comuns, determinando quais são aceitáveis para um adequado monitoramento sismográfico. Dessa forma, foi estudada a influência de quatro métodos de fixação nos parâmetros de vibração. Para este propósito, o primeiro geofone foi colocado sob um saco de areia, o segundo foi enterrado no solo, o terceiro foi cravado no solo e o quarto foi livremente colocado sobre o solo. Estes geofones foram dispostos lado a lado e as vibrações de desmontes com explosivos de uma mina de carvão a céu aberto foram monitoradas. As vibrações foram analisadas em termos de velocidade de vibração de partícula de pico, históricos temporais e frequência associada à vibração. Os resultados obtidos indicaram o desacoplamento do geofone sob saco de areia, descartando o método. O enterramento do geofone se mostrou preferível, entretanto, o uso de cravos registrou bom acoplamento. A colocação do geofone sobre o solo se mostrou aceitável de acordo com o nível de aceleração de vibração, decorrente do desmonte. / The main environmental impacts from rock blasting are ground vibrations and air overpressure. For proper blast vibration monitoring, it is critical that the sensor be coupled to the medium, enabling accurate measurement of ground vibration. Due to the existence of several recommendations regarding the mounting of vibration sensors (geophones) in the field, this study intends to evaluate the most common geophone coupling methods, determining which are acceptable for adequate vibration monitoring. The influence of four mounting methods on vibration parameters was studied. For this purpose, the first geophone was sandbagged, the second one was buried in soil, the third one was spiked and the fourth one was placed freely on the ground. These geophones were mounted side by side and ground vibrations at an opencast coal mine were monitored. The vibrations were analyzed in terms of peak particle velocity, time histories and frequency spectra. The results indicated the decoupling of the sandbagged geophone, discarding the method. The burial of the geophone proved to be preferable, however, the use of spikes recorded good coupling. The free placement of geophone proved to be acceptable according to the expected acceleration level.

Interaction of various components in rotating machinery like gearboxes may generate excitation forces at various frequencies. These frequencies may sometimes overlap with the frequencies of the forces generated by other components in the system. Conventional vibration spectrum analysis does not attenuate noise and spectral frequency band overlapping, which in many applications masks the changes in the structural response caused by the deterioration of certain components in the machine. This problem is overcome by the use of time domain averaging (dsynchronous averaging). In time domain averaging, the vibration signal is sampled at a frequency that is synchronized with the rotation of the gear of interest and the samples obtained for each singular position of the gear are ensemble-averaged. When sufficient averages are taken, all the vibration from the gearbox, which is asynchronous with the vibration of the gear, is attenuated. The resulting time synchronously averaged signal obtained through this process indicates the vibration produced during one rotation of the monitored gear. This direct time domain averaging process essentially acts as a broadband noise synchronous filter, which filters out the frequency content that is asynchronous with the vibration of the gear of interest provided that enough averages are taken. The time domain averaging procedure requires an enormous amount of vibration data to execute, making it very difficult to develop online gearbox condition monitoring systems that make use of time domain averaging to enhance their diagnostic capabilities since data acquisition and analysis cannot be done simultaneously. The objective of this research was to develop a more efficient way for calculating the time domain average of a gear vibration signal. A study of Artificial Neural Networks (ANNs) and Support Vector Machines (SVMs) was conducted to assess their suitability for use in time domain averaging. Two time domain averaging models that use ANNs and SVMs were developed. Model 1 uses a single feedforward network configuration to map the input which are rotation synchronized gear vibration signals to the output which is the time domain average of the gear vibration signal, using only a section of the input space. Model 2 operates in two stages. In the first stage, it uses a feedforward network to predict the instantaneous time domain average of the gear vibration after 10 inputs (10 rotation synchronized gear vibration signals) to predict the instantaneous average of the gear rotation. The outputs from the first state are used as inputs to the second stage, where a second feedforward network is used to predict the time domain average of the entire vibration signal. When ANNs and SVMs were implemented, the results indicated that the amount of gear vibration date that is required to calculate the time domain average using Model 1 can be reduced by 75 percent and the amount of gear vibration data that needs to be stored in the data acquisition system when Model 2 is used can be reduced by 83 percent. / Dissertation (M Eng (Mechanical and Aeronautical Engineering))--University of Pretoria, 2006. / Mechanical and Aeronautical Engineering / unrestricted